Polyurethane Concrete Sealant

Originally polyurethane concrete sealants were all solvent based; however, today you can also buy a more environmentally friendly type of polyurethane concrete sealer that is water based. Either way, by using polyurethane concrete sealants you will render what was a porous surface non-porous.

This not only means that you can prevent water penetration into the concrete surface but, if traffic is moving or parked on top it or machinery is used above it, you can also prevent oils and other chemicals from penetrating the surface.

Polyurethane concrete sealers will also prevent any staining on the surface, whilst if the concrete is colored enhancing its appearance. Finally, and of particular importance in a workshop or where pedestrians are walking, polyurethane sealants when applied to a concrete surface will also provide a non-slip surface.

Preparing to Use Concrete Sealant

The concrete surface being treated must be as clean, dry and dust free as possible. Polyurethane sealers do not mix well with water during application, so any surface water must be removed and the sealer must not be applied until any dampness in the concrete has dried out. This can be particularly tiresome if the concrete to be sealed is outdoors and the weather is bad, as any dampness in contact with the sealant before it has properly dried out will impair its effectiveness.

Tell-tale white patches when the sealant has dried will reveal areas that were damp to start with. The surface needs to be as clean as possible too, as if the sealant is applied over loose particles of concrete, when the particles are knocked away untreated surface will be exposed that can be penetrated by water, oil etc.

Should there be any damaged areas of concrete these need to be patched before applying the sealant. Although clearing a concrete surface completely of dust is not realistic, even if there are no obvious particles on the surface of the concrete it should be brushed thoroughly before applying a polyurethane concrete sealer.


Polyurethane concrete sealers can be applied with a brush or a spray gun system. However, using a brush is to be recommended as you will have greater control over obtaining a covering that is more consistent and better worked in to the surface, whether over a large or small area. A soft brush is recommended and a 5 liter can of sealant should cover about 40 sq. meters.

As indicated above, if you’re applying the sealant outdoors, it must not be applied if it is raining or if there is likely to be rain within 24 hours of applying it, which is its nominal drying time. If the concrete surface is an old and friable one you’ll get the best results by first applying a coat of a moisture cured binder sealant, followed by 2 coats of the polyurethane concrete sealant itself.

For better concrete surfaces you can apply an undercoat/primer made by mixing 85% of the concrete sealant and 15% of a thinner, followed by two coats of the pure sealer. Applied properly a polyurethane concrete sealant will prove incredibly durable.

Polyurethane concrete sealants can be bought as a colorless lacquer or colored paints. Both will do exactly the same job in keeping the concrete free from stains, easy to clean and creating a safety-first non-slip surface. Using colored polyurethane concrete sealers would be a great idea in a workshop where you want to make it clear that designated areas are for specific tasks.